OF FERRUGINOUS BODIES. 219 
saw, and not more than two inches wide, the 
motions of the disturbed pole will, generally, be 
from the point of heat: but as the temper of the 
metal has much to do with the lateral movements 
of the poles, a hard temper will sometimes cause 
a temporary movement towards the point of heat, 
after which the polar transplacements are uni- 
formly from the point of heat. 
30. When the magnetized plate is hard, more 
than one-twentieth of an inch thick, and upwards 
of two inches broad, the first movement of the 
disturbed pole is almost sure to be towards the 
point of heat; and if the lamp be suddenly re- 
moved to the opposite side of that pole, the latter 
will return to its former position in the steel, pass 
over that portion, and again approach the point 
of heat, until the deflected needle indicates a 
pause. 
31. The pole will now move no nearer to the 
point of heat, but will retrograde a little. Ifnow 
the spirit lamp be brought to its first position, the 
needle again indicates a movement of the pole in 
the steel, which may now be either towards the 
lamp or from it, according to the direction of the 
prevailing force. 
